A prominent cause of deafness is loss of hair cells due to age, noise or antibiotic treatments. In contrast to mammalian hair cells, fish, bird and amphibian hair cells are constantly turning over and regenerate following hair cell death. The aim is to take advantage of the lateral line of zebrafish to define and characterize the molecular and cellular interactions occurring during hair cell regeneration with the long-term goal of activating these pathways in mammals. To uncover the mechanisms driving hair cell regeneration, the lateral line of the zebrafish was chosen as an experimental paradigm because of 1) the ability of zebrafish support cells to regenerate hair cells;2) the functional and morphological similarity between the lateral line hair cells and the hair cells of the inner ear;3) its accessibility to direct observation and manipulation throughout development;and 4) the ability to rapidly and cost-effectively isolate specific cell types involved in hair cell regeneration, experiments that are difficult to perform in the classical model systems, e.g., mouse and chick. The two laboratories are pursuing the following strategy to identify the earliest genes that are transcribed in support cells subsequent to hair cell death. First, the location and population dynamics of stem cells and surrounding niche cells in normal and regenerating neuromasts will be determined, which is essential for determining the signals required for stem cell maintenance and activation. Secondly, the transcriptome of purified support cells will be defined using microarray analyses. To systematically analyze all candidate genes identified, a novel and powerful bioinformatics approach will be employed to identify genes co-regulated by the same transcription factors. Identifying these important transcription factors will be crucial for our understanding of how regeneration is triggered in lower vertebrates. Combined, these two approaches will discover key hair cell regeneration genes and set the stage for a systematic dissection of this complex problem to inform the development of therapeutics to regenerate hair cells in mammals. PUBLIC HEALTH RELEVANCE: Stem cells are crucial for adult tissue homeostasis and regeneration. The zebrafish lateral line is an excellent model to elucidate the genetic pathways controlling stem cells and sensory hair cell regeneration. Results from our studies will aid in the identification of stem cells in the mammalian ear and in the development of therapeutic strategies to regenerate hair cells in mammals.